gistfile1.rb

require 'ffi'

module Exec
  extend FFI::Library

  attach_function :my_exec, :execl, [:string, :string, :varargs], :int
  attach_function :fork, [], :int
end

vim1 = '/usr/bin/vim'
vim2 = 'vim'
if Exec.fork == 0
  Exec.my_exec vim1, vim2, :pointer, nil
end

Process.waitall